This invention relates to an electrolytic process and apparatus where the performance of an electrolyte is maintained by limiting electrode-derived contamination formed during the process and more particularly to a process and apparatus including an electrode compartment to restrict the electrode-derived contamination from adversely effecting the bulk electrolyte and cathode materials. The invention further relates to a process and apparatus using the electrode compartment where the feed is introduced into the compartment to improve the efficiency of the process.
Electrolytes of special importance are those used in the electrolytic reduction of metal oxides where the reaction of oxide ions at the anode results in liberation of CO and CO.sub.2 and may result in the physical separation of particles from the anode. Usually the electrolytes are molten inorganic salts with the anode being carbon (often graphite). During operation of the process, particles of carbon separated from the anode float to the electrolyte surface. In the aluminum refining industry, skimming devices have been used to remove these particles because they may electrically short the cell or otherwise adversely affect the electrical performance of the cell.
The problem is also evident in other electrolytic processes involving the recovery or reusable metals from radioactive metal oxide compositions. One such process at a developmental stage involves the electrolytic reduction of calcium oxide in a CaCl.sub.2 -CaF.sub.2 electrolyte where the anode is a consumable carbon electrode and the cathode is a molten metal pool such as Cu-Mg or Zn. The electrolytic process is part of an overall chemical process where the calcium and clean electrolyte regenerated in the electrolytic process are utilized to reduce uranium oxide, transuranium (TRU) element oxides, and fission product oxides in spent reactor fuel. The reduced TRU elements may be used as a fuel for a fast reactor, and the uranium may be stored for ultimate use as a fertile blanket material in a fast reactor. In the chemical reduction process, the calcium is converted to calcium oxide which becomes dissolved in the CaCl.sub.2 -CaF.sub.2 salt and is recycled to the electrolytic process.
During operation of the process to recover elemental calcium and salts, carbon particles from the anode contaminate the electrolyte and may interfere with the operation of the electrolytic process by causing shorting. These particles may also react with cathode material in the cell or with fuel material if transferred with the electrolyte into the reduction step. Accordingly, one object of the invention is an improved electrolytic process and associated apparatus. A second object of the invention is the development of associated apparatus and process to limit electrode-derived contamination of the electrolyte in an electrolytic process. Another object of the invention is apparatus and associated electrolytic process to maintain the performance of the electrolyte in the process. An additional object of the invention is apparatus and associated electrolytic process to limit adverse reaction between electrode-derived contaminates and materials in the electrolyte. A further object of the invention is an improved process and apparatus for reducing a metal oxide. These and other objects will become apparent from the following detailed description.